1. Field of the Invention
The present invention relates to a location-relevant service; in particular, the present invention relates to a location-relevant service accessible by multiple mobile devices.
2. Discussion of the Related Art
Location-relevant services, which provide information or perform services based on the geographical location of a mobile client, are becoming more available. A location-relevant service can be used, for example, by a trucking company to track the positions of its vehicles in service. Another application of location-relevant systems is to provide travel-related services (e.g., driving directions) based on the position of the client. One example of a location-relevant service is described, for example, in copending U.S. patent application “Method for Distribution of Locality-Relevant Information using a Network” (“Copending Application”), application Ser. No. 09/422,116, filed Oct. 20, 1999. To provide an example regarding the architecture and application of a location-relevant information system, the disclosure of the Copending Application is hereby incorporated by reference in its entirety.
Typically, a location-relevant system includes a location-relevant service server accessible by multiple mobile units over a communication system, which includes wireless links to the mobile units. The mobile units provide their positions based on a positioning system. The position of a mobile unit can be provided by, for example, the Global Positioning System (GPS) or, in a cellular telephone network, by a process called triangulation which is based on signal delays from system base stations of known fixed locations. Due to technology limitations at the present time, it is costly to integrate the capabilities of both positioning and wireless communication of such a mobile unit into a hand-held device. In addition, hand-held positioning devices are also typically less accurate than their more sophisticated bulky counterparts. Therefore, a mobile unit in a location-relevant service is typically fixedly installed on a vehicle. However, a mobile unit fixedly installed on a vehicle cannot provide the convenience and mobility of a hand-held unit.
Another desirable application that is not known in the prior art is accessing from a mobile unit location-relevant service based on the position of another mobile unit.